Multihull Structure Thoughts

Discussion in 'Multihulls' started by oldmulti, May 27, 2019.

  1. Burger
    Joined: Sep 2017
    Posts: 41
    Likes: 19, Points: 8
    Location: Australia

    Burger Junior Member

    As aerodynamic as a block of flats............
    Some 20 years ago a local named Mal Hone built a "cruiser" SW24. Being an experienced multihull sailor and boatbuilder, he did it properly. Sterns were extended to make her 26', a low solid bridgedeck was added, just big enough to enclose an athwartships double bunk. Bridgedeck clearance was slightly better than standard, additions were all light foam/glass and suitably streamlined.
    Mal eventually sold her, and Chica's new owner had a trouble-free 9-day delivery run from Airlie Beach to Darwin.
     
    ALL AT SEA likes this.
  2. oldmulti
    Joined: May 2019
    Posts: 2,563
    Likes: 1,637, Points: 113
    Location: australia

    oldmulti Senior Member

    United States National Library of Medicine says 1 in 3 people are considered highly susceptible to motion sickness. Servo Yachts LLC offers revolutionary electric suspension system that stabilizes catamarans to eliminate motion that can cause seasickness. The company founded by David Hall, who founded Velodyne Lidar, he invented the 3D lidar vision system that spawned some autonomous vehicles and advanced robotics.

    The electric suspension system connects the yacht's superstructure to two dynamic hulls which adjust in real-time to the height and angle of the waves, keeping the deck in a level position and absorbing the roll, pitch and heave motions induced by the ocean. The design also causes less drag than on traditional yachts, resulting in a remarkably efficient vessel that is not only safe and comfortable, but faster in rough conditions.

    “With the Martini 7.0, I believe we have found a way to solve seasickness and significantly improve the sailing experience so that everyone can enjoy traveling on the ocean. I am very excited for Servo Yachts to continue to push the boundaries of marine technology and transform ocean travel. Ideas for better ways to do things are always out there floating around, and it's up to us to find a way to make it happen."

    “Martini 7.0 is a 165 foot catamaran with up to 12 foot of vertical travel in each hull. The result is a vessel that can move at speed through an ocean swell with virtually no motion in the suspended deck where the crew and guests are located.” Orion Shuttleworth, Managing Director of Shuttleworth Design.

    A series of smaller prototype vessels ranging from 17 foot to 45 foot, that have been developed and tested in San Francisco Bay by Servo Yachts to develop the Servo Yacht system. The suspension system adjusts to feedback received in real-time based on a computer-automated electro-pneumatic mechanical system. This technology is an active method and is much more effective than current passive marine stabilisation devices which take more time to react to the motion of the sea. The system requires very little power and no warm-up time or complex vacuum systems, making it the most immediate, effective and safe option.

    The jpegs give the idea. The web sites to look at are: Servo Yachts https://www.servo-yachts.com/ and Servo Yachts https://www.shuttleworthdesign.com/Servo-Yachts.php
     

    Attached Files:

    Last edited: Jul 26, 2022
  3. oldmulti
    Joined: May 2019
    Posts: 2,563
    Likes: 1,637, Points: 113
    Location: australia

    oldmulti Senior Member

    Originally a British company, Prout catamarans are now built in China. The 45 S is an older design done in the 1990’s. The Prout 45 S is 45 x 23 foot with a weight of 21,500 lbs and a displacement of 26,500 lbs. Both these numbers appear a little light especially with the gear on board these boats but these are the quoted numbers. The draft is 4 foot over fixed low aspect ratio keels. Now we get to the rig. There are two 60 HP Volvo Penta engines. The standard Prout 45 S rig is a fractional sloop with 1,184 square foot of sail area in a fairly conventional mast position. At least 2 of the Prout 45 S ended up with Aerorigs on them.

    The resulting comments are: “FELIX was commissioned and sea trialled in Ft Lauderdale in April 1997. The Prout 45 is renown for its sea worthiness and kindly manor, this yacht has been further enhanced to make short handed sailing more of a pleasure than it normally is with the UPGRADED AERORIG, all major systems have back ups, the oversized winches make sail handling a dream, imagine tacking by turning the helm and nothing else!! 100% Visibility (no ducking) under sail etc etc. FELIX is fully equipped for offshore short-handed sailing, the simplicity of the AERORIG design gives you the ultimate in safety, simplicity, and performance.”

    The accommodation of the owner’s version has the port hull to the owners with master cabin, and head with separate shower stall and numerous hanging lockers. The guest suite has its own en-suite head/shower and across the Forward saloon there is a very attractive and practical day berth. Large saloon features all round visibility a circular table and cocktail cabinets etc. In the Starboard hull is the well-equipped ‘open’ galley is along side the salon so you are not ‘cut off’ and features, 4 burner stove, propane oven refrigerator and a freezer, forward of the galley is a washer dryer with further guest sleeping in a double cabin forward. Cockpit with seating at the table for 6 with the cockpit as a whole seating 12, the large bimini covers the whole cockpit which can also be also enclosed with screens and curtains making it an all weather area and helm station. There’s more wood than we’ve used to seeing in catamarans and the factory has done its best to keep weight down with extensive use of cored moldings.

    Beyond a few comments I could not find any information about performance but one could assume with the Aerorig an easily handled cat which would do about half windspeed. The Jpegs give some idea with the last jpeg a standard rig Prout 45.
     

    Attached Files:

  4. oldmulti
    Joined: May 2019
    Posts: 2,563
    Likes: 1,637, Points: 113
    Location: australia

    oldmulti Senior Member

    Befoil 16 is a simple foiling catamaran designed by VPLP especially for sailing schools and beginners. Built from components by various French suppliers, Befoil 16 is claimed to be a perfect boat for those new to foiling being stable, simple to manoeuvre and safe. The Befoil is 16 x 8.2 foot with removable hiking racks which extend the beam to 14.1 foot. The weight of the standard Befoil 16 is 515 lbs with a 129 square foot mainsail and a 40 square foot jib on a 24.6 foot rotating mast. The Befoil 16 Sport is 392 lbs with a 150 square foot mainsail and a 40 square foot jib on a 24.6 foot rotating mast. The maximum suggested crew weight is 320 lbs. The draft when the foils are down is 3.3. foot. The T foils are retractable.

    The foils are controlled by forward wands and flaps on the main foils as per Moth monohulls. This approach to foiling is easier to sail as the cat automatically adjusts to the sea conditions while foiling. This style of foil design also is harder to design initially but results in an easier to sail cat. The latest eg A class foilers do not have flaps on the foils and are designed for higher top speed but require the helmsperson to manually “adjust” the rake of the fore or aft foils to suit varying conditions. Aluminium foils lower susceptibility to impact and abrasion gives it better durability than carbon for amateur use, especially on the beach. Titanium parts are nevertheless machined for the junction of the vertical and horizontal profiles of the foils.

    Why the difference of weight between the 2 versions? The method of construction. The standard Befoil 16 has rotomolded hulls whereas the Befoil 16 Sport has vinylester resin infused foam e-glass hulls. Both models have the same aluminium foils and rig bar the larger fat head mainsail in the Befoil 16 Sport. The result of the weight difference is shown in the performance. The standard Befoil 16 will take off onto it foils in 10 knots of true wind speed. The Befoil 16 Sport will take off in 8 knots of true wind speed and can reach over 20 knots of boat speed in the right conditions. The cross beams are aluminium and are bolted to the hulls.

    I admire the French for developing a cat to train people for foiling boats of all types. Foiling requires differing skills to obtain the best results, its not too much harder, but understanding the apparent wind shifts and the skills required to “fly” through a tack etc need to be learned to avoid a few swims. A top Moth foiling skipper versus an average Moth sailor can be the length of a leg of a course.

    The jpegs give the idea.
     

    Attached Files:

  5. oldmulti
    Joined: May 2019
    Posts: 2,563
    Likes: 1,637, Points: 113
    Location: australia

    oldmulti Senior Member

    This is about a cruising cat by Malcom Tennant that is being discussed on another thread. Timeliner is 46 x 24.8 foot bridgedeck performance ocean cruising cat that weighs 14,000 lbs fitted out with half full tanks and displaces up to 18,000 lbs. The rig is a fractional rig with a 55 foot fixed aluminium mast that carries 1150 square foot of sail area. The basic draft is 3 foot to 7.5 foot when the daggerboards were down.

    Timeliner has 2 double berth cabins and a toilet in each hull. The main saloon has a full galley, dinette, navigation and entertainment centre all with full headroom. This boat is a serious cruiser that can sail well.

    The build came in several formats depending on when the cat was built. The original design had 13mm cedar and 440 gm unidirectional on each side doubled over the exterior bottom all in epoxy resin. An owner put an additional layer of 400 gsm biaxial below the waterline (not specified by Tennant). The original main beam was 6 mm ply, 25 mm balsa, 6 mm ply with timber framing. The rear beam was 6 mm ply, 20 mm balsa, 6 mm ply with timber framing. The mid bulkhead beam 4 mm ply, 25 mm Styrofoam, 4 mm ply with timber framing. The furniture and foam glass ring frames added additional stiffening to the hulls. Later versions of Timeliner had the same hulls but had foam glass bulkheads instead of the timber balsa versions.

    The comments from another thread. Ross Pelham re Tennant 47' cat Timeliner build. "Pahia hull construction was 13mm cedar and 440 gm unidirectional on each side, sounds lightweight I know but was fine,I put an extra layer of 400 db below WL each side for beaching loads on skeg, not specified by Malcolm, total boat weight 5.9 t fitted out with half full tanks ,she had two queen berth 2 double and 2 swr /wc ,would be interesting what the displacement of a new boat build would be under today's spec! Most people are shocked when i tell them the planks were 13mm but she is very strong with no panel bigger than 1m x 2m with furniture and foam glass ring frames elsewhere,Tennant knew his stuff and I built exactly to plan except cabin shape which i modernized, I built that one at Coomera in Peter O'Briens shed in 1999"

    This is a fast performance cruiser that is designed and built to be long and light with thin hulls and a moderate rig for best performance, it is not designed to carry large loads with a huge sail area to compensate for the additional weight. Built as designed, you will be a very happy person if you can find one.

    The jpegs tell the story.
     

    Attached Files:

  6. jamez
    Joined: Feb 2007
    Posts: 563
    Likes: 65, Points: 28, Legacy Rep: 231
    Location: Auckland, New Zealand

    jamez Senior Member

    Sorry missed this when current. Flat (or flattish) hull bottoms seem to becoming quite common. The Grainger TR36 main hull is essentially dory shaped with rounded chines.

    upload_2022-7-31_9-24-10.png
     
    guzzis3 and oldmulti like this.
  7. oldmulti
    Joined: May 2019
    Posts: 2,563
    Likes: 1,637, Points: 113
    Location: australia

    oldmulti Senior Member

    Ray Aldridge designed a 16 foot day cat called Slider which proved to be popular. Ray does not consider himself to be a naval architect but a designer who builds cats for himself then sells plans if they work well. Ray then conceived a 14 foot, simpler to build, day cat called Slipper which is more a cruising day cat than a racer. The Slipper is 14 x 7 foot that weighs 255 lbs and a maximum displacement of 700 lbs. The cat has a 105 square foot spirit mainsail on a short stayed mast. The hulls at the gunnels are 2 foot wide with 1.5 foot of hull height in the original build. The draft started as 1 foot with fixed rudders on aft skegs. There was no daggerboards or keels on the original build.

    As I said, Ray builds a proof of concept cat first and develops it a bit. The Slipper went through quite a development cycle. We will deal with the rig, rudders and lateral resistance first prior to the construction. The rig proved to be relatively reliable only requiring some fine tuning on the mast base and sail cut (polytarp) to start. The sheeting angles etc were refined a bit. Next came the rudders. The original design was a shallow “barndoor” unbalanced rudder with a long blade aft attached to a skeg. The cat did not steer well or tack easily. The next addition was a horizontal fence on the bottom of the rudder blade, which only slightly improved the steering. The cat still did not tack, turn, balance or go to windward well. Ray then tried some much deeper kickup rudders and found the cats steering was improved but upwind performance was not good.

    Ray had found on his 16 foot Slider design the Slider could go to windward well without any additional foils, depending on the dory hull shape to provide resistance. So, he thought he could achieve the same thing on the 14 foot Slipper. Due to the lack of upwind performance, Ray decided to try chine runners on the hull but that did not work to satisfaction. Ray then built a simple centrally mounted centreboard out of Styrofoam with 3 layers of 200 gsm glass cloth wrapped around and a plywood head insert for the pivot point and resistance point on the bridgebeck. Slipper was transformed into a good handling cat that would tack and tack between 100 degrees and track well. A complete transformation. As Ray said this is the reason, he builds prototypes.

    The concept of Slipper was to be a much simpler to build “car toppable” cat for those who did not have the time or desire to build a bigger cat. Ray left out or minimised any part of the design he could. Result a very well conceived hull structure that worked well. 6 mm plywood over 2 bulkhead frames (attached to the cross beams) and a transom. There are 25 x 18 mm outwales (gunnels) and taped chines. There was no fore or aft decks. The cross beams are a plywood web with 20 mm timber top and bottom. The underwing is ply. After initial sailing Ray wanted to add fore decks and after decks as the freeboard proved to be to low. His initial idea of connecting the hulls and beams with rope did not work out and he developed a pin connection system for disassembly. Ray finally thought the cat could be trailed easier than assembled and disassembled.

    Ray finally gave away the plans for Slipper for free for a short will before Ray had problems with pirating of his Slider plans in Germany. After his web site was hacked, I think Ray lost interest in developing further boats and went back to being a studio potter. Rays 16 foot Slider design was very good, Rays Slipper design was heading in the right direction and with further development could have been very good. We all have learnt something from his development work.

    The jpegs give an idea of the development of the Slipper.
     

    Attached Files:

    guzzis3 and Flotation like this.
  8. redreuben
    Joined: Jan 2009
    Posts: 1,999
    Likes: 223, Points: 63, Legacy Rep: 349
    Location: South Lake Western Australia

    redreuben redreuben

    I’m aware, hence the question.
    Ok, I realise they are easier to build, I’m aware they provide cheap displacement. But …… they have higher wetted surface, ride like a *****, have lower panel strength so have to be built heavier and in my experience hard chines are more vulnerable to damage so I’m not convinced.
    Mostly because here (Perth) we have lots of short steep wind against current chop.
    I’m not looking for a racer so I want good displacement with a nice ride.
    catamaran 24-28 feet
     
  9. oldmulti
    Joined: May 2019
    Posts: 2,563
    Likes: 1,637, Points: 113
    Location: australia

    oldmulti Senior Member

    A short one from Kurt Hughes. Kurt has a sample plan package that give some interesting insights into various components of some of his signs. I especially liked his kickup rudder, daggerboard and case details in 23 foot tri sample plan. Also his woodwing mast plan gives an interesting view of how to possible build one. The engine room arrangement and the structure required to support engines in a 55 foot cat is also interesting. It is worth taking a close look at the PDF as it provides a few insites.

    And I have not forgotten the stressform mast instructions and pyramid rigs. Life is a little busy around here.
     

    Attached Files:

    Flotation likes this.
  10. oldmulti
    Joined: May 2019
    Posts: 2,563
    Likes: 1,637, Points: 113
    Location: australia

    oldmulti Senior Member

    Robert Biegler. I have found 2 of the articles about Pyramid rigs from Practical Boat Owner oct 1976 and feb 1976 (it took a long search). The pages are shown below in the jpegs. The first article explains the theory of the rig and its useability. The second article is a test sail from Jim Andrews who has done a lot of cruising catamaran sailing on Prout and Catalac catamarans. He was also a professional writer. His has sailed a conventionally rigged Prout as well as the Pyramid rig conversion model and found them to similar in performance even thought the Pyramid rig only had 75% of the sail area of the standard rig.

    Please remember, Chefren the cat featured, originally had the "Pyramid Rig". The rig failed after some sailing (unknown details) and a standard Snowgoose 34 rig was fitted just before it was sold.

    Please read the jpegs for further details.
     

    Attached Files:

    Flotation and peterbike like this.
  11. oldmulti
    Joined: May 2019
    Posts: 2,563
    Likes: 1,637, Points: 113
    Location: australia

    oldmulti Senior Member

    The Gypsy 28, a Richard Woods designed budget catamaran, comes in several versions and materials. The reason for the discussion is Redrueben desire the benefits of round bilge versus chine version hulls. The Gypsy is 28 x 17.7 foot with a weight of 4000 lbs if built in ply and a displacement of 5400 lbs. The weight varies according to build technique. Some Gypsy’s weighed 3500 lbs at launch in foam triaxle epoxy and carbon rigs, others were 4400 lbs if build in heavy ply. The 32 foot fixed aluminium mast standard rig carries 410 square foot. Draft depends on the keel type. The fixed keel draws 2.8 foot. The daggerboard option depended on the builder but about 5 foot is realistic.

    Now we get to the issue here. Gypsy is a cruiser that can sail well if built to plan. But Richard Woods provides many versions of the plan. The standard version is a hard chine dory hull shape with a V forward built in ply. Next came a ply version with a round bilge bottom in strip plank WRC with the same cross beams and pod cabin. Next was a foam glass version with the same dory hulls and a V forward with varying degrees of foam glass or ply above the gunnel level. The there are round bilge foam glass versions that are mainly foam glass throughout. Starting to understand the weight variations. The most “interesting” version is a Dutch built Gypsy "Tweebaksman" that has a dory hull built from in corecell/epoxy/tri- and quadraxial glass sandwich with a rotating carbon fibre mast and boom with dyneema shrouds. Remember this is basically a budget cruising cat design, yes you get a better payload capability because of the light build, but it would be expensive to build.

    Now we get to the hull shapes. From the readings I have done most Gypsy sailors are happy with the seakeeping and sailing performance of their Gypsy. The most famous longest distance sailing Gypsy “Lightwave” had a 4 foot rear extension to its hulls to get a better waterflow. Lightwave is a heavier build that is loaded for long term live aboard cruising. Lightwave owner said it improved its performance. To my limited knowledge, no Gypsy owner has modified the forward V sections of the dory hull shape. The round bilge versions would have slightly less wetted surface and may have a better ride through a seaway but there are other factors at play.

    Richard Woods has stated that a good daggerboard over a fixed keel will compensate for any performance losses because of a well designed chine hull. A good set of sails will do the same. If the total displacement of the cat is reduced it will have the same effect. If the hull is cleaned regularly and has good antifoul it will have more effect than a round bilge over a chine hull. What I am saying I have sailed on chine, deep V, deep round bilge and shallow round bilge hulls. If the design was well balanced, they were all “comfortable” to sail through a seaway. The real issue is how full the ends were. Fuller ends pitch less but can “pound” more in a seaway. One of the harder riding 42 foot cats I was on had 14 to 1 length to beam hulls but very full ends. It was very fast upwind but the full round bilge hull forward pounded more than finer deep V hulls forward. Spindrift 37 and 45 foot cats have a smooth motion with their fine V end hulls but many added on fuller sterns and bulbs to the bows. The modified Spindrifts were harder riding but faster upwind. Basically, its up to a person to understand what is acceptable for them. I find I am uncomfortable on fine ended cats, but harder riding less pitching fuller ended hulls causes less discomfort in a seaway to me.

    Finally, the build differences between a hard chine and a round bilge can be a decision point. Flat glass panels that are resin infused or plywood panels hulls are relatively fast and easy to build BUT getting the chine lines to look smooth is not always easy. Round bilge strip plank WRC of foam glass if done carefully will visually look better but will take more time to build. Please remember that hulls are between 10% to 20% of a total build time, so on a 4000 hour build you may only spend an extra 400 hours doing a round bilge hull for a minimal gain in sailing performance. BUT there will be a significant difference in the resale value between a ply chine hull and a round bilge foam glass hull.

    The jpegs give an idea of the hull variations of a Gypsy. A nice budget cruiser with many variations. The last 4 jpegs are "Tweebaksman", the lightweight foam glass Gypsy.
     

    Attached Files:

    fallguy and bajansailor like this.
  12. redreuben
    Joined: Jan 2009
    Posts: 1,999
    Likes: 223, Points: 63, Legacy Rep: 349
    Location: South Lake Western Australia

    redreuben redreuben

    I hear you Oldmulti I hear you.
     
  13. Robert Biegler
    Joined: Jun 2017
    Posts: 166
    Likes: 87, Points: 38
    Location: Trondheim

    Robert Biegler Senior Member

    Thank you. Low sheet loads, easy depowering on any course, and containing all the forces needed to maintain sail shape within the rig are also reasons why some people have chosen the Balestron rig. The pyramid rig might be easier to build, lacking a boom that takes large bending loads. The editor of Practical Boat owner praised the easy reefing. Chefren getting a conventional rig before sale could be due to that attracting a larger potential pool of buyers, so if the boat was to be sold anyway, a replacement rig was needed, and price was similar, the experimental rig was clearly not the way to go. I can find only two reasons for the pyramid rig's lack of popularity (I can count only eight boats that tried it, and I am sure there have been more Balestron rigs): poor light wind performance, and the extreme sensitivity to angle of attack mentioned by Norwood.
     
  14. oldmulti
    Joined: May 2019
    Posts: 2,563
    Likes: 1,637, Points: 113
    Location: australia

    oldmulti Senior Member

    This is about a very adventurous man and his cats. Beto Pandiani who decided to cruise around the world on beach cats. He started on the Hobie 16’s in Brazil, then in 1989 he was crowned North American Champion in at Chicago. In the 90’s he sailed from Miami to Ilha Bela near Sao Paulo Bazil, It took 289 days to complete the 13.000 kms voyage. In 2000 he and his crew sailed from Chile to Rio via Cape Horn on a Hobie 21. A 170 day trip crossing one of the toughest regions on the planet. They become the first sailors passing the Cape Horn on a boat without cabin. In 2003 the challenge was even tougher he and his crew sailed the Drake Passage to Antartica. 500 miles on a 23 foot open beach cat. Next was a 2007-2008, trip to cross the Pacific from Chile-Australia with Igor Bely a new longer term crew. 17.000kms, with weeks with no land at hand. The cat used here was the Eagle Ocean 24 (seen in some jpegs below). In 2012 the challenge was crossing the 7,000kms from South Africa to Brazil again with Igor Bely as crew. The “Cape Town-Rio” was non stop. The Eagle Ocean 24 is a specially designed is an open bridge deck carbon fibre and foam “beach cat” with hiking racks.

    Now at 64 Beto Pandiani and Igor Bely are currently sailing a new cat across the Northwest Passage. The trip is proposed to take 100 days (he is on day 48 now). So what tough cat is he taking on this trip? Do you remember a cat called Felix rom Turning Point design for the Race to Alaska? “Felix” the Turning Point 24 foot (now 26 foot) carbon fibre foam is a camp “cruiser” racing catamaran. Felix is 24 x 10 foot weighing 750 lbs and when ready for the water in racing trim with 2 crew and 300 lbs water ballast displaces about 1400 lbs. The carbon fibre rotating wing mast is 34 foot (ex Farrier 25 C) carrying 350 square foot mainsail area and a jib/genoa upwind. With the crew racks for the overall “beam” is 16 foot. On Page 26, 100 and 122 describes Turning Points evolution.

    This is close to a “beach cat” for an Artic trip across the Northwest Passage. I have no question about Beto and Igor’s sailing skill or bravery but Felix the cat is a very thin skin carbon fibre racing cat. Hitting a log in the Race to Alaska is a different thing to forcing your way through 1000’s of kilometres of an ice laden passage. Also, the race to Alaska is a 15 day adventure with stops as wanted. A 100 day Northwest Passage requires a lot more stores and safety equipment to be loaded onto a very light cat. The virtue of Felix is it has a small cubby cabin to get some rest in a very cold environment.

    If you have the courage and skill, you can sail almost anything across an ocean but there are increasing risks the smaller the cat and the more exposed you are whilst sailing. You can die in 20 minutes if you fall into very cold water, you can die of hypothermia if you are wet sitting in the wind in minus temperatures. Small cats with big rigs can capsize easily in big seas etc. Please be careful out there. The jpegs give the idea of some of the cats.
     

    Attached Files:

    fallguy and bajansailor like this.

  15. peterbike
    Joined: Dec 2017
    Posts: 74
    Likes: 25, Points: 18
    Location: melbourne

    peterbike Junior Member

    Thanks oldmulti for going to the trouble to track down the pyramid rig articles.
    Thanks also to the guy who asked about it.
    This rig with a little modernisation could make a cheap practical cruising rig :)
    Especially with a quiver of spinnakers at the ready.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.